I just don’t see it. If we look at THT’s advanced fielding stats, we see that Zimmerman has a substantial lead over Kouzmanoff in plays made. He also has more in-zone chances. If we give Kouz the same number of opportunities in his zone as Zimmerman has, Kouzmanoff would indeed be 3 plays better than Zimmerman. However, Zimmerman would still have 45 more out-of-zone plays than Kouzmanoff. So, they are similar with balls hit in the BIS-defined third base zone, but Zimmerman makes a bunch more plays outside of that zone.

By the way, Zimmerman’s UZR is at +16 runs, while Kouzmanoff is at +6. Kouz has had a good season in the field by most measures, and his fielding percentage is impressive, but I’m not really sure that he’s anything more than an average defensive third basemen.